The ninja arrive in the world of the hunger games. When they arrive they are taken by the captive by the capital and brought directly to Snow. They choose not to show they're power knowing a gun could kill them just as easy. It's during the time of the hunger games and the male tribute in district 12 was hurt so Snow makes a deal. One of the ninja take their place and participate in the hunger games in exchange for letting them live and go home. They agreed not really understanding what the hunger games are. (I do not own either franchise and cover image is not mine credit for cover image goes to SerpentNinja and I have read the books but I am going off the movies, because when I need reference it is easier to look to the movies. This is also something that just came to me some chapters are short compared to others and please no negative comments because I know this is not my best work)